skip to main content
US FlagAn official website of the United States government
dot gov icon
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
https lock icon
Secure .gov websites use HTTPS
A lock ( lock ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.


Title: Linking marine core lithofacies and mineral and grain-size compositions on the Baffin Island margin: changes in provenance and transport
We evaluate the linkages between lithofacies and mineral composition of late Quaternary sediments along the Baffin Slope for cores 2013029 64, 74, and 77. Four major lithofacies were identified: diamicton (L1), laminated red-brown mud (L2), tan carbonate mud (L3), and brown bioturbated mud (L4). In addition, goldbrown mud (L2a) beds were identified within red-brown mud throughout the Baffin margin and a thin, locally distributed light gray mud (L2b), also identified within red-brown mud, was localized to the Home Bay region. A classification decision tree (CDT) correctly predicted ~ 87% of the lithofacies based on five binary choices based on the estimated weight %s of (in order): quartz, kaolinite, plagioclase, iron oxides, and smectites. The detrital tan carbonate (DC) minerals, calcite and dolomite, did not appear in the chosen CDT solution although this lithofacies is easily recognized in cores because of its tan color and the facies is well predicted in the CDT. The addition of grain size did not substantially improve the prediction of the lithofacies although it did change the % importance of the minerals in the CDT.  more » « less
Award ID(s):
1804504
PAR ID:
10181646
Author(s) / Creator(s):
; ;
Date Published:
Journal Name:
Journal of sedimentary research
Volume:
90
ISSN:
1073-130X
Page Range / eLocation ID:
1-13
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. We combine geomorphological and sediment core evidence to investigate phases of ice margin stability and instability during retreat of the Boothia Lancaster Ice Stream (BLIS) of the NE Laurentide Ice Sheet (LIS) since the Last Glacial Maximum (LGM). Sediment cores 2008029-059 PC and TWC (59CC) and 2013029-064 PC (64 PC) from Lancaster Sound and Baffin Bay, respectively, represent LGM through Holocene environments, including three Baffin Bay Detrital Carbonate (BBDC) events that have been thought to manifest calving events within Lancaster Sound. Previous mapping of glacigenic landforms shows that 64 PC lies within the LGM limit of the convergent BLIS and Tasiujaq Ice Stream (TIS) on the northeastern Baffin Island shelf, while 59CC terminates within subglacial/ice marginal sediments termed the Baffin Shelf Drift (BSD), capturing the history of BLIS retreat from 15.3 cal ka BP onward. In 64 PC, a basal sediment gravity flow deposit is overlain by dolomite-rich BBDC 2, which is re-interpreted here as a subglacial/ice marginal deposit and renamed GZ-BBDC. Both gravity flows are interpreted to have formed during retreat of the confluent TIS and BLIS from the LGM maximum extent. Overlying GZ-BBDC, in 64 PC, is a finely laminated lithofacies interpreted as an ice-shelf facies formed beneath the ice shelf fronting the confluent TIS and BLIS when it occupied a large LGM grounding zone wedge (GZW) in northern Baffin Bay. The ice-shelf facies indicates temporary stabilization of the conjoined TIS and BLIS. The overlying thin black glaciomarine diamicton records disintegration of the ice shelf and retreat of the TIS. Ice retreat over Cretaceous and younger bedrock into Lancaster Sound is recorded by dark brown diamicton and glaciomarine sediments in 59CC. The overlying tan, detrital carbonate-rich glaciomarine diamicton, BBDC 1 in 59 PC, manifests calving retreat of the BLIS onto the Paleozoic carbonate bedrock within Lancaster Sound by 15 cal ka BP. A slightly later onset of BBDC 1 in 64 PC, of ca.14.5 cal ka BP, points to the influence of local conditions such as sea ice and local iceberg calving on the distribution of IRD off of Pond Inlet. The pause in ice rafting and detrital carbonate deposition between BBDC 1 and BBDC 0 within the Younger Dryas chron likely results from BLIS readvance to Devon Island and its stabilization there until 11.6 cal ka BP. BLIS retreat into Prince Regent Inlet marks the onset of BBDC 0. These new results indicate multiple periods of instability of the BLIS, which are responsible for BBDC events identified throughout Baffin Bay. 
    more » « less
  2. Lead (Pb) solubility is commonly limited by dissolution–precipitation reactions of secondary mineral phases in contaminated soils and water. In the research described here, Pb solubility and free Pb2+ ion activities were measured following the precipitation of Pb minerals from aqueous solutions containing sulfate or carbonate in a 1:5 mole ratio in the absence and presence of phosphate over the pH range 4.0–9.0. Using X-ray diffraction and Fourier-transform infrared spectroscopic analysis, we identified anglesite formed in sulfate-containing solutions at low pH. At higher pH, Pb carbonate and carbonate-sulfate minerals, hydrocerussite and leadhillite, were formed in preference to anglesite. Precipitates formed in the Pb-carbonate systems over the pH range of 6 to 9 were composed of cerussite and hydrocerussite, with the latter favored only at the highest pH investigated. The addition of phosphate into the Pb-sulfate and Pb-carbonate systems resulted in the precipitation of Pb3(PO4)2 and structurally related pyromorphite minerals and prevented Pb sulfate and carbonate mineral formation. Phosphate increased the efficiency of Pb removal from solution and decreased free Pb2+ ion activity, causing over 99.9% of Pb to be precipitated. Free Pb2+ ion activities measured using the ion-selective electrode revealed lower values than predicted from thermodynamic constants, indicating that the precipitated minerals may have lower KSP values than generally reported in thermodynamic databases. Conversely, dissolved Pb was frequently greater than predicted based on a speciation model using accepted thermodynamic constants for Pb ion-pair formation in solution. The tendency of the thermodynamic models to underestimate Pb solubility while overestimating free Pb2+ activity in these systems, at least in the higher pH range, indicates that soluble Pb ion-pair formation constants and KSP values need correction in the models. 
    more » « less
  3. A gas hydrate assessment at International Ocean Discovery Program Expedition 400 drill sites was conducted using downhole logging and core data. Here, we calculate and present the base of gas hydrate stability zone at Expedition 400 drill sites in Baffin Bay, northwest Greenland. We used data from downhole logs and sediment cores from Sites U1603, U1604, U1607, and U1608 to assess hydrate and did not find evidence for the presence of hydrate. At Site U1606, only core data were acquired that showed a decrease in pore water salinity, potentially indicating the presence of hydrate; however, further confirmation was not possible due to the unavailability of downhole logging data. Because of the limitation of the acquired data at the drill sites, a further assessment to confirm the presence of hydrate was not possible. Although hydrate was not identified at any drill sites, hydrate might still be present in the region. 
    more » « less
  4. Nares Strait, a major connection between the Arctic Ocean and Baffin Bay, was blocked by coalescent Innuitian and Greenland ice sheets during the last glaciation. This paper focuses on the events and processes leading to the opening of the strait and the environmental response to establishment of the Arctic‐Atlantic throughflow. The study is based on sedimentological, mineralogical and foraminiferal analyses of radiocarbon‐dated cores 2001LSSL‐0014PCandTCfrom northern Baffin Bay. Radiocarbon dates on benthic foraminifera were calibrated with ΔR = 220±20 years. Basal compact pebbly mud is interpreted as a subglacial deposit formed by glacial overriding of unconsolidated marine sediments. It is overlain by ice‐proximal (red/grey laminated, ice‐proximal glaciomarine unit barren of foraminifera and containing >2 mm clasts interpreted as ice‐rafted debris) to ice‐distal (calcareous, grey pebbly mud with foraminifera indicative of a stratified water column with chilled Atlantic Water fauna and species associated with perennial and then seasonal sea ice cover) glacial marine sediment units. The age model indicates ice retreat into Smith Sound as early asc. 11.7 and as late asc. 11.2 cal. kaBPfollowed by progressively more distal glaciomarine conditions as the ice margin retreated toward the Kennedy Channel. We hypothesize that a distinctIRDlayer deposited between 9.3 and 9 (9.4–8.9 1σ) cal. kaBPmarks the break‐up of ice in Kennedy Channel resulting in the opening of Nares Strait as an Arctic‐Atlantic throughflow. Overlying foraminiferal assemblages indicate enhanced marine productivity consistent with entry of nutrient‐rich Arctic Surface Water. A pronounced rise in agglutinated foraminifers and sand‐sized diatoms, and loss of detrital calcite characterize the uppermost bioturbated mud, which was deposited after 4.8 (3.67–5.55 1σ) cal. kaBP. The timing of the transition is poorly resolved as it coincides with the slow sedimentation rates that ensued after the ice margins retreated onto land. 
    more » « less
  5. null (Ed.)
    This study investigated the reaction kinetics on the oxidative transformation of lead( ii ) minerals by free chlorine (HOCl) and free bromine (HOBr) in drinking water distribution systems. According to chemical equilibrium predictions, lead( ii ) carbonate minerals, cerussite PbCO 3(s) and hydrocerussite Pb 3 (CO 3 ) 2 (OH) 2(s) , and lead( ii ) phosphate mineral, chloropyromorphite Pb 5 (PO 4 ) 3 Cl (s) are formed in drinking water distribution systems in the absence and presence of phosphate, respectively. X-ray absorption near edge spectroscopy (XANES) data showed that at pH 7 and a 10 mM alkalinity, the majority of cerussite and hydrocerussite was oxidized to lead( iv ) mineral PbO 2(s) within 120 minutes of reaction with chlorine (3 : 1 Cl 2  : Pb( ii ) molar ratio). In contrast, very little oxidation of chloropyromorphite occurred. Under similar conditions, oxidation of lead( ii ) carbonate and phosphate minerals by HOBr exhibited a reaction kinetics that was orders of magnitude faster than by HOCl. Their end oxidation products were identified as mainly plattnerite β-PbO 2(s) and trace amounts of scrutinyite α-PbO 2(s) based on X-ray diffraction (XRD) and extended X-ray absorption fine structure (EXAFS) spectroscopic analysis. A kinetic model was established based on the solid-phase experimental data. The model predicted that in real drinking water distribution systems, it takes 0.6–1.2 years to completely oxidize Pb( ii ) minerals in the surface layer of corrosion scales to PbO 2(s) by HOCl without phosphate, but only 0.1–0.2 years in the presence of bromide (Br − ) due the catalytic effects of HOBr generation. The model also predicts that the addition of phosphate will significantly inhibit Pb( ii ) mineral oxidation by HOCl, but only be modestly effective in the presence of Br − . This study provides insightful understanding on the effect of residual disinfectant on the oxidation of lead corrosion scales and strategies to prevent lead release from drinking water distribution systems. 
    more » « less